In the name of allah, the Beneficent, the Merciful What is sin in Islam?

The first impression gained by the reader is not the one suggested by the Shafi'ites. It is only wishfully that one can extract from the verse the meaning that the animal slaughtered without Allah's name having being taken over it is clean.
Secondly, if joining a declarative nominal to an optative verbal sentence infringes the elocutionary principles, the use of the emphatic irma and the intensifying 1am is no less a breach of the rules of elocution. If Allah had to say what the Shafi'ites say, the wording would have been: (i.e. in case of its being abomination) AND NOT (in case of its most certainly being abomination).
Thirdly, in their passion for argument, the Sha6'ites fail to keep the complete verse in mind. The verse reads:
And eat not of that whereon Allah's name has not been mentioned, for lo ! it is abomination. Lo ! the devils do inspire their minions to dispute with you. But if you obey them, you will in truth be idolaters.

Now even if it is granted that the waw in it is abomination !

is circumstantial, the problem of a declarative nominal sentence joined to an optative verbal sentence persists, for the sentence which follows right after is clearly declarative, is incapable, of being made into a circumstantial sentence, and is necessarily joined to the optative sentence. Moreover, this is not the solitary instance of its kind to be found in the Quran. At a number of places, a declarative nominal has been joined to an optative verbal sentence, as for example in verse 4 of The Light

…flog them with eighty stripes; and reject their evidence ever after: for such men are wicked transgressors;

And in verse 221 of The Cow.'

Do not marry unbelieving women until they believe: a slave woman who believes is better than an unbelieving woman. Even though she allure you. Nor marry (your girls) to unbelievers until they believe: a slave man who believes is better than an unbeliever even though he allure you.

The Shafi'ites must either revise their elocutionary doctrines or declare that the Quran violates the principles of elocution. For it is not possible at each place in the Quran to take the maw joining an optative verbal to a declarative nominal sentence as the waw of circumstance.